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SubjectRE: [PATCH v4 05/12] iommu/vt-d: Reserve a domain id for FL and PT modes
Date
Hi Baolu,

> From: Lu Baolu [mailto:baolu.lu@linux.intel.com]
> Sent: Monday, November 5, 2018 1:32 PM
> Subject: [PATCH v4 05/12] iommu/vt-d: Reserve a domain id for FL and PT modes
>
> Vt-d spec rev3.0 (section 6.2.3.1) requires that each pasid
> entry for first-level or pass-through translation should be
> programmed with a domain id different from those used for
> second-level or nested translation. It is recommended that
> software could use a same domain id for all first-only and
> pass-through translations.
>
> This reserves a domain id for first-level and pass-through
> translations.
>
> Cc: Ashok Raj <ashok.raj@intel.com>
> Cc: Jacob Pan <jacob.jun.pan@linux.intel.com>
> Cc: Kevin Tian <kevin.tian@intel.com>
> Cc: Liu Yi L <yi.l.liu@intel.com>
> Cc: Sanjay Kumar <sanjay.k.kumar@intel.com>
> Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
> ---
> drivers/iommu/intel-iommu.c | 10 ++++++++++
> drivers/iommu/intel-pasid.h | 6 ++++++
> 2 files changed, 16 insertions(+)
>
> diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
> index 9331240c70b8..2f7455ee4e7a 100644
> --- a/drivers/iommu/intel-iommu.c
> +++ b/drivers/iommu/intel-iommu.c
> @@ -1618,6 +1618,16 @@ static int iommu_init_domains(struct intel_iommu
> *iommu)
> */
> set_bit(0, iommu->domain_ids);
>
> + /*
> + * Vt-d spec rev3.0 (section 6.2.3.1) requires that each pasid
> + * entry for first-level or pass-through translation modes should
> + * be programmed with a domain id different from those used for
> + * second-level or nested translation. We reserve a domain id for
> + * this purpose.
> + */
> + if (sm_supported(iommu))
> + set_bit(FLPT_DEFAULT_DID, iommu->domain_ids);

"FLPT_DEFAULT_DID" looks very likely for first level translation. How about
"PT_FL_DEFAULT_DID"?

> return 0;
> }
>
> diff --git a/drivers/iommu/intel-pasid.h b/drivers/iommu/intel-pasid.h
> index 12f480c2bb8b..03c1612d173c 100644
> --- a/drivers/iommu/intel-pasid.h
> +++ b/drivers/iommu/intel-pasid.h
> @@ -17,6 +17,12 @@
> #define PDE_PFN_MASK PAGE_MASK
> #define PASID_PDE_SHIFT 6
>
> +/*
> + * Domain ID reserved for pasid entries programmed for first-level
> + * only and pass-through transfer modes.
> + */
> +#define FLPT_DEFAULT_DID 1

Would be helpful to elaborate why DID 1 is selected in the patch
description.

Regards,
Yi Liu

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